One way that consumer routers compete is on features. No doubt, the vendors think people will buy the router with the most features.
But features can be bad. The less software that's running, the safer you are. Techies refer to this as reducing the attack surface.

What follows is a list of router features that most people can turn off most of the time. If you need it, fine. But, if not,
turn it off.

Every router will not have every feature listed below and there will be times when a certain feature can not be disabled.

UPnP and NAT-PMP are two different protocols that do the same thing - they let devices on your network poke holes in the router firewall. This makes setup of some new devices easier, but is a huge security hole. It is how IoT devices make themselves visible on the Internet, where many of them get hacked, either due to security flaws or the use of default passwords. UPnP was from Microsoft, NAT-PMP was developed by Apple. Many routers only support UPnP, Apple routers support NAT-PMP and higher end routers support both. Turning these protocols off may break something. If it does, then you need to make a choice: either live dangerously or setup the necessary port forwarding manually.

Remote administration. This is the function that lets someone on the Internet access the web interface of the router. It is also commonly called "Remote Management" and there may be other terms for it, such as "Web Access" too. Peplink calls is "Web Admin Access." See
examples from TRENDnet and Cisco.

Telnet access to the router on both sides (WAN and LAN). An October 2016 study by ESET found
that Telnet access was available from the LAN side in more than 20% of the 12,000 routers they tested. See a
screen shot of disabling Telnet on a Verizon DSL gateway.
In May 2018, it was reported that an ISP in Brazil shipped routers with Telnet enabled and no password. You can't make this stuff up.

IP version 6 (a.k.a. IPv6) then test that it is really off at whatismyv6.com. In 2013 someone discovered a bug
in IPv6 regarding fragmentation buffer overflow. Just having IPv6 enabled made you vulnerable.

Sharing of devices plugged in to a USB port, if possible. File sharing may be referred to as SAMBA. The NetUSB flaw left an untold number of routers vulnerable to attack.
Asus in particular has had multiple problems sharing files in a USB port. Asus owners should consider turning off all three AiCloud features: 'Cloud Disk,' 'Smart Access,' and
'Smart Sync'. Quanta routers were found to have four
backdoor accounts in Samba.

FTP. In July 2018 a design flaw with FTP in Netgear routers led to the leaking of military documents. No hacking was needed, the owners of thousands of Netgear routers do not change default passwords. The Netgear KB articles on FTP configuration are shameful in their ignoring security issues. Coverage of the hacking is on the Router News page under July 2018.

Access to the web interface on ports 80 and 443. That is, always administer the router via a non-standard port

Cloud based management. This relatively new feature competes with Remote Administration, it is another way to administer a router. The company
that makes the router will offer a cloud management website from which anyone who knows the password can re-configure the router. To me, this means
trusting every employee of the router vendor. No thanks to that.

VPN passthrough for PPTP VPNs. PPTP is the least secure type of VPN, this insures you don't use it. If you don't use a VPN at all, then also
turn off passthrough for the other types of VPNs.* But, you should use a VPN, even at home.

VPN server(s)

Bonjour

DLNA Media server and/or DLNA media sharing

iTunes server

DDNS (Dynamic DNS) If doing Remote Administration, this may be needed.

DMZ. It places computers virtually outside the router firewall. It should be off by default, but you should check it every now and then in case
router was hacked. See an Asus UI sample.

Port Forwarding. Should be off by default. That said, there are defensive measures that do port forwarding to known bad IP addresses, so
this feature can swing both ways. Note than TRENDnet calls this feature "virtual server"

WiFi whenever possible, such as overnight. If you are very lucky, the router can schedule this. If you are somewhat lucky, there will be an on/off
button for WiFi.

RIP v1, aka Routing Information Protocol version 1. Probably not installed, as the protocol is extremely old, but if its there, turn it off. It is more
likely to be installed on routers running
DD-WRT.

If you are using the Google OnHub router, turn off the features that deal with "smart devices", that is: Bluetooth Smart Ready,
Weave and 802.15.4.

AirPrint

*On episode 510 of the Security Now! podcast, Steve Gibson read an interesting note from a
listener who had turned off all VPN passthrough on a router. Sure enough, a user on the network was using a VPN, but the story is more interesting than
that. Search the transcript for "Nathan in Kansas". The episode aired June 2, 2015.